Conventional electrical power generation systems are generally limited in terms of the rate at which the power generation hardware can transition from one power output level to another; this transition from a first power output level to a second power output level is generally referred to as a “ramp rate.” The theoretical limit on ramp rate is affected by the physical characteristics and architectural implementation of the equipment used to generate the electrical power, and may be influenced by a variety of factors including some or all of the following: the size, volumetric capacity, and operating pressures of boilers; the size and operational parameters of steam turbines; the rotational inertia, magnetic characteristics, and efficiency of electric generators; or a combination of these and many other factors.
Additionally, there is generally a latency or lag between a ramp request and system output that corresponds to the output level requested (the “setpoint”). In practical electricity generation applications, there is always a delay between a control input and a power level output that satisfies the level required or requested by the control input. The extent of this latency (i.e., the duration of the lag) is influenced by the factors mentioned above, in addition to others. It takes time for fluid to boil responsive to added heat, it takes time for pressures to increase as a result of expanding fluids, and it takes time for a turbine to accelerate to a steady state in response to increased pressure. Even in the case where a single electricity generator, or a single generation facility, is capable of handling a specific load at steady state, it is often the case that such a single unit cannot ramp fast enough to accommodate instantaneous load demands. Running such a single unit at a higher output level than required at any particular moment (e.g., in anticipation of higher loads in the future) is generally not efficient and undesirable.
Irrespective of any physical, mechanical, or materials science limitations related to the equipment itself (based, for example, on critical pressures or “never-exceed” rotational velocities that might cause mechanical damage or catastrophic system failure), and ignoring any theoretical limitations on ramp rate, equipment manufacturers often limit the rate at which an electricity generation system or apparatus may be stressed; the manufacturers do this via documentation or other product literature suggesting or recommending a maximum sustained rate (or “MSR”) for each particular implementation of their products. Such published documentation often takes into account conservative engineering safety margins, wear and tear and associated maintenance costs, the possibility of negligence or abuse on the part of the operating entity, liability insurance premiums, and other factors that combine artificially to reduce the recommended MSR well below the operational capabilities of the equipment itself.
Utility companies have installed and currently operate many electricity generation facilities throughout the country. To satisfy customer demands, many of these facilities either employ a plurality of generators, operate in concert with each other, or both. In accordance with conventional technology and traditional techniques, it is generally necessary to bring more resources on line in the short term to handle transient loads than are necessary to handle the steady state load in the long term. Thus, there is a need for precise, discrete (i.e., per unit) MSR control functionality that provides an improved and enterprise-wide response to transient load demands while making efficient use of local system resources.